JP2682099B2 - Easily soluble baking soda and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an easily soluble baking soda and a method for producing the same, and particularly to an easily soluble and easy-to-handle baking soda suitable for use in pharmaceutical products such as hemodialysis fluid or foods. Is.

(Prior Art) Baking soda is generally handled as a powder, and it is required to have various powder characteristics such as fluidity, particle size, bulk specific gravity, and solubility depending on the application.

As a method for producing these baking sodas, a method of precipitating sodium bicarbonate crystals by bicarbonate of an aqueous solution containing sodium carbonate or by cooling a solution containing sodium bicarbonate is common.

(Problems to be Solved by the Invention) However, the baking soda obtained by these methods is likely to be needle-shaped or plate-shaped, and since it is fine particles, it has poor fluidity, has a low bulk specific gravity, and is difficult to handle. Was common.

Among these physical properties, fluidity is an important factor in handling in each application. Therefore, it has been proposed to use a habit modifier, for example, as a material for improving the fluidity, or to control the shape and size of the crystal by specifying the precipitation conditions and the like. (For example, JP-B-48-17160, JP-A-55-60021, JP-A-60-
However, although these methods are certainly effective in improving the fluidity, they have the drawback that the dissolution rate and reaction rate are markedly reduced for applications in which dissolution or reaction is performed. doing.

It is also considered to improve both the fluidity and the solubility by granulating baking soda with an organic binder, but in this case the problem that the organic binder remains in the granulated product There is a point.

(Means for Solving the Problem) The present inventor has conducted various studies and studies for the purpose of eliminating the drawbacks of these conventional methods and obtaining baking soda having both sufficient fluidity and easy solubility. As a result, they have found that the above objects can be achieved by making baking soda into granules having specific physical properties. Thus, the present invention is a granular baking soda which does not contain an organic binder and is substantially composed of baking soda, and in which crystalline primary particles are cohesively bonded, and the dissolution time thereof is not more than 3 times the dissolution time of the primary particles. And a wear rate of 50% or less and a repose angle of 50 degrees or less, and a method for producing the same.

In the present invention, the dissolution time is defined as follows.
Put 500 ml of water in a beaker with a capacity of 1 and keep it at 25 ° C.
While stirring at pm, add 50 g of sample to a beaker,
The time when the% is dissolved is defined as the dissolution time. The dissolved amount is obtained by periodically sampling a portion of the solution while agitating the solution and analyzing it.

The wear rate is defined as follows. 30 g of sample to 100
Or, put it in one of the standard sieves (diameter 20 cm) of 65 or 32 mesh, sieve it lightly, and
The next particles were removed and the weight of the remaining particles was measured.
And Next, the surface of the sieve is kept horizontal while the particles are put on the sieve, and the surface of the sieve is vibrated at 200 rpm for 1 hour so as to draw a circle having a diameter of 15 mm in parallel. Due to this vibration, the particles that were crushed on the sieve and passed through the sieve were weighed and designated as B.
The ratio of B / A is displayed in%, and this is taken as the wear rate. Here, the sieve is selected according to the particle size as follows. Measure the particle size distribution of the secondary particles in advance and from the smaller particle size, 10% by weight
The particle size corresponding to is calculated. If the particle size is less than 210μ, use a 100 mesh screen. The particle size is 210μ or more
If it is less than 500μ, use a 65 mesh screen. If the particle size is 500μ or more, use a 32 mesh screen.

The angle of repose is based on the bottom-only method. In the present specification, it is a value measured by a powder tester manufactured by Hosokawa Micron Co., Ltd.

Thus, the baking soda according to the present invention has a composition of substantially baking soda without containing an organic binder, and is in the form of granular baking soda (hereinafter referred to as secondary particles) in which crystalline primary particles (hereinafter referred to as primary particles) are cohesively bonded. Has become. The granular baking soda of the present invention preferably contains 97% by weight or more, and preferably 99% by weight or more of baking soda. In the present invention, the components other than baking soda which may be present in the primary particles are sodium carbonate or sodium sesquicarbonate.

The crystalline primary particles constituting such baking soda have a particle size of 100.
It is preferable that the particles of μ or less are 60% by weight or more, and desirably 90% by weight or more. The greater the number of primary particles having a particle size of more than 100 μ, the higher the wear rate and the longer the dissolution time.

Further, when the average aspect ratio of the primary particles is 4 or less, more preferably 2 or less, it is possible to prevent the wear rate from decreasing, which is preferable.

The easily soluble granular baking soda according to the present invention has a physical property that the dissolution time is not more than 3 times that of the primary particles.
When the dissolution time exceeds 3 times, the solubility is too low as compared with the primary particles, which is not suitable.

Also, the wear rate must be 50% or less. This is 50
If it exceeds%, the secondary particles are disintegrated during the handling process such as transportation to become the primary particles themselves, and the particles are scattered, making it difficult to handle at the time of use.

Also, the angle of repose should be 50 degrees or less. When the angle of repose exceeds the above range, the fluidity is deteriorated, and it becomes difficult to uniformly mix with other solid materials, which is not suitable.

The average particle diameter of the secondary particles is preferably 0.1 to 5 mm. If the average particle size is less than the above range, the fluidity is poor, and conversely, if it exceeds the above range, the abrasion strength may decrease, which is not preferable.

As a method for producing the easily soluble granular baking soda of the present invention,
For example, the following method is preferable.

First, a raw material baking soda powder consisting of crystalline primary particles is mixed with a liquid so as to have a water content of 0.5 to 10% by weight, and granulated.
If the amount of water added is less than the above range, the wear rate of the secondary particles becomes large, and conversely, if it exceeds the above range, granulation becomes difficult, which is not preferable.

Water can be used as the liquid added at the time of granulation, but when a liquid that forms an aqueous solution of sodium carbonate is formed as the liquid phase existing between the primary particles of the granulated product, it is used in the drying step described below. The sodium carbonate in the aqueous solution reacts with carbon dioxide gas between primary particles of baking soda to deposit new baking soda, and the bond strength between the primary particles is improved, so that the wear rate can be reduced, which is preferable.

The concentration of this aqueous solution is effective even if it is colored with phenolphthalene, but it is effective to adjust the concentration of carbonate to 1 to 19% by weight. An aqueous solution of sodium carbonate is preferable as this liquid. Even when an aqueous solution of caustic soda is used, sodium hydroxide reacts with primary particles of sodium bicarbonate during granulation to form an aqueous solution of sodium carbonate between the primary particles, so that the same effect as using the aqueous solution of sodium carbonate can be obtained from the beginning. be able to. Similarly, an aqueous solution of sodium sesquicarbonate or the like can be used.

As specific granulation means carried out under such conditions, for example, wet rolling granulation and extrusion granulation are suitable, and primary particles are broken or compressed and solidified as in granulation by a compression molding method. Such means is not preferable because the dissolution time becomes long.

The granulated particles are then dried in a carbon dioxide gas atmosphere to obtain the easily soluble granular baking soda of the present invention. in this case,
As the carbon dioxide concentration in the carbon dioxide atmosphere, it is appropriate to adopt 5% or more for the purpose of preventing decomposition of sodium bicarbonate during drying and sufficiently causing bicarbonate of the sodium carbonate content. In this case, it is appropriate to adopt a drying temperature of about 30 to 90 ° C.

Specific drying means carried out under such conditions include, for example, a band dryer, a batch-type box dryer, a disk dryer, an aeration dryer, a rotary dryer and the like.

(Example) An average particle size of 50μ obtained by a known method,
90% of particles having a particle size of 100μ or less are present, and 0.71 Kg of sodium carbonate aqueous solution containing 12% by weight of carbonate root is added to 10 kg of primary particles of sodium bicarbonate crystals having an average aspect ratio of 2, and the water content of baking soda is 5% by weight. Mixed so that Next, this was granulated using a twin-screw type extrusion granulator to obtain a granulated product having an average particle size of 400μ. Next, the granulated product was placed in a hot air circulation type dryer adjusted to a carbon dioxide gas concentration of 20% and a temperature of 50 ° C. and dried for 3 hours.

As a result, baking soda composed of granular secondary particles was obtained. Its average particle size was 0.4 mm, dissolution time was 1.3 times that of raw baking soda (primary particles), wear rate was 3% measured using a standard 65 mesh sieve, powder from Hosokawa Micron Co., Ltd. The angle of repose measured by a tester was 38 degrees. The secondary particles were not pulverized by normal handling, were easy to handle when dissolved, and were extremely easily dissolved in water at 25 ° C.

Claims (7)

(57) [Claims] 1. Crystalline primary particles (hereinafter referred to as primary particles) which are substantially composed of sodium bicarbonate and do not contain an organic binder.
Are cohesively bonded granular multilayers (hereinafter referred to as secondary particles), the dissolution time of the secondary particles is 3 times or less than the dissolution time of the primary particles, the wear rate is 50% or less, and the angle of repose is Soluble baking soda with a melting point of 50 degrees or less. 2. Primary particles are 60 particles having a particle size of 100 μm or less.
The baking soda according to claim 1, wherein the baking soda is at least wt%. 3. The baking soda according to claim 1 or 2, wherein the average aspect ratio of the primary particles is 4 or less. 4. The baking soda according to claim 1, wherein the secondary particles have an average particle size of 0.1 to 5 mm. 5. A crystalline primary particle consisting essentially of baking soda,
A method for producing a readily soluble baking soda, which comprises mixing and granulating with a liquid so that the water content is 0.5 to 10% by weight, and drying in a carbon dioxide gas atmosphere. 6. The method according to claim 5, wherein the liquid to be mixed is a liquid which forms an aqueous solution of sodium carbonate as a liquid phase existing between the primary particles of the granulated product when mixed with sodium bicarbonate. 7. The method for producing baking soda according to claim 5, wherein the granulation method is extrusion granulation.